Engineered pinhole-stitching process of PEI-based hollow fiber membrane enables preferred performance toward light gas separation

Abstract

The hollow fiber configuration, comparing to flat-sheet and tubular modules, have gained much attention in a gas separation field due to its exceptionally high packing density. However, the decline in inherent selectivity exhibited by specific shape (namely hollow fiber) would result from the existence of pin-hole in its skin layer of hollow fiber. Hence, the post-treatment for the modification of pin-hole is crucial for this eye-catching configuration. Herein, the effects of bare fiber pore structure and corresponding post-treatment parameters including the concentration of modifier and modification method on the morphologies and permeation properties of the resultant membranes were investigated. The enhanced performance of polymeric hollow fiber after dip-coating in 6 wt. % polydimethylsiloxane (PDMS) solution was observed, which was due to modification of pin-hole. Subsequently, while the method of post-treatment was changed from dip-coating to internal coating, the hydrogen permeance had been increased by 3–4 times, benefiting from the less PDMS intrusion into the fiber pores. Meanwhile, its excellent separation factor toward H2/CH4 pair up to 65 also was showcased, confirming the presence of selective inner surface. In conclusion, this work provides a facile post-treatment to advance the gas transport capability of polymeric hollow fiber as well as maintaining the inherent permeance as maximum.